The bike was badly neglected over the last 16 years -- it has 1.600 miles, and spent long periods -- years -- without any use.

I cleaned the carbs (and intalled new float needles and gaskets and o rings), and reinstalled them. Hooked them up to a remote, gravity feed tap/tank from my 75 Commando, as the T900 tank is badly rusted and I am not finished cleaning and sealing it.

Fired up pretty quickly and ran strong for about 5 minutes, then slowly died out and would not restart. I heard a gurgling sound from the airbox while it was running (which I had cleaned out when I reintalled the carbs.)

Is the vacuum line to the tap (which I did not block off) screwing up the fuel flow?

Duck bill was clear (at least, I could blow air through the fuel intake), at least when I fired her up.

The second line is probably the overflow that fits to the rear of the T-bird tank. It might be an idea to check for a spark when it heats up, could be something getting hot and failing, i.e the pickup coil or ignition coil, but 5 mins is probably not long enough for that to happen.

The bike was badly neglected over the last 16 years -- it has 1.600 miles, and spent long periods -- years -- without any use.

I cleaned the carbs (and intalled new float needles and gaskets and o rings), and reinstalled them. Hooked them up to a remote, gravity feed tap/tank from my 75 Commando, as the T900 tank is badly rusted and I am not finished cleaning and sealing it.

Fired up pretty quickly and ran strong for about 5 minutes, then slowly died out and would not restart. I heard a gurgling sound from the airbox while it was running (which I had cleaned out when I reintalled the carbs.)

Is the vacuum line to the tap (which I did not block off) screwing up the fuel flow?

Duck bill was clear (at least, I could blow air through the fuel intake), at least when I fired her up.

Get it running on the remote, and then when it starts to idle down, turn the petcock off and hold the rpms up for 20 seconds or so with the throttle. If she idles clean with the petcock off, but the problem comes back when you turn the gas back on, it's the floats / float valves / o-rings (which you replaced, but I replaced mine a month ago and she's doing it again. If you used the GSXR rebuild kit, the o-rings are just a hair thick, which seems to cause problems in the short term.)

Adjusting the float levels on these is a bit of a pain. Don't know about the Mikunis, but with the Keihins you let the tab touch the little nipple that compresses, but don't let it compress.
You can test them for flooding on the bench as well, by hooking up your fuel line to each one individually, and letting the gas into the float bowl and then see if it begins leaking by.
I have found even the tiniest bit of rust specks are enough to mess up the needle valve or the jets, so if there is any possibility that any sediment could have gotten into the carbs (possibly dried up in the fuel lines and then reconstituted when the fuel went through the line?), it could be the problem. Put a clean hose on the fuel bowl drains and drain them onto a white paper towel. Any gunk will be visible.

Get it running on the remote, and then when it starts to idle down, turn the petcock off and hold the rpms up for 20 seconds or so with the throttle. If she idles clean with the petcock off, but the problem comes back when you turn the gas back on, it's the floats / float valves / o-rings (which you replaced, but I replaced mine a month ago and she's doing it again. If you used the GSXR rebuild kit, the o-rings are just a hair thick, which seems to cause problems in the short term.)

a slightly cracked vacuum line has been enough to keep my engine from starting in the past. Quick trip to autozone and a couple snips later had me good as gold again. here's to hoping it is a simple a fix for you.

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